Conventionally, as a method for connecting a member-to-be-connected to a pipe, the following method, for example, is known.
A pipe is inserted into a pipe insertion hole formed in a member-to-be-connected, and an expanding die is placed in a hollow portion of the pipe. This die is divided into a plurality of die segments in the circumferential direction thereof centering around a wedge hole portion formed in the central portion of the die. Next, a wedge portion of a mandrel is inserted into the wedge hole portion of the die to thereby move each die segment of the die in the radially outward direction of the pipe. With this, the inserted portion of the pipe inserted in the pipe insertion hole and both axially adjacent portions of the inserted portion are subjected to an expanding process (i.e., diameter enlarging process) to thereby connect the member-to-be-connected to the pipe. This connecting method is also called a ridge lock processing method (see, for example, Patent Documents 1 to 3).
In this connecting method, both the axially adjacent portions of the inserted portion of the pipe inserted in the pipe insertion hole are locally pressed outwardly of the pipe from the inside of the pipe by two pressing protruded portions of the die segments, locally forming a pull-out preventing expanded portion (diameter enlarged tubular portion) at each of the axially adjacent portions. The member-to-be-connected is connected to the pipe in a state in which the member-to-be-connected is clamped by and between these two expanded portions. With this, the pull-out joint strength of the member-to-be-connected to the pipe is enhanced. Therefore, it is important to expand both the adjacent portions of the pipe to enhance the pull-out strength of the pipe.    Patent Document 1: Japanese Unexamined Laid-opened Patent Application Publication No. H4-8818 (page 2, FIG. 8)    Patent Document 2: Japanese Unexamined Laid-opened Patent Application Publication No. H11-36859    Patent Document 3: Japanese Unexamined Laid-opened Patent Application Publication No. H7-223030 (paragraphs [0004] to [0007], FIGS. 5 to 7)